The present invention relates generally to the field of oceanographic sensors, and more particularly to expendable oceanographic sensors. Sensors of this type are typically deployed in a large body of water, such as an ocean, and remain there for a substantial period of time taking measurements of predetermined water characteristics. For example, such sensors may be deployed from an airplane (by parachute) or from a surface vessel, and may remain in the water for periods of as much as two years, or more.
There are numerous indicia of water phenomena which are of value either to oceanographers in general, or to the captain and crew of surface or subsurface vessels. For example, water temperature, depth, conductivity, optical properties, nutrient availability, etc., may provide valuable information for a number of divergent uses. This information may be used to expand the knowledge base of ocean parameters in general, or may be useful in navigation, sonar communication and the like.
There are numerous apparatus, available to measure various ocean parameters. For example, U.S. Pat. No. 4,953,986, Olson et al., discloses a device to detect air and water surface temperatures beyond the thermal influence of a ship underway at sea. The device accounts for the surface evaporation duct at the air/water interface, which can cause refraction of electromagnetic radiation propagated through it, thereby adversely affecting radio communication, radar and radio navigation transmissions. The device comprises a temperature transducer formed as bifilar wire looped several times around an electrically nonconductive open frame. The resistance of the wire corresponds to ambient temperature. A signal processing network detects the resistance of the wire and provides an electrical pulse modulated output functionally related to the resistance.
Another device is disclosed in U.S. Pat. No. 4,924,698, wherein remote monitoring of oceanographic conditions is accomplished through the use of remote buoys or sensors. Water temperature, salinity and pressure are measured and transmitted to a remote location. The device is affixed to pack ice in the arctic or antarctic, with a sensor package affixed to a cable extending downwardly a fixed distance. The sensor package is provided with a wing, permitting it to move up and down the cable. The depth of the sensor package may be varied at will by adjusting the pitch of the wing relative to the ocean current.
Still another expendable oceanographic probe is disclosed in U.S. Pat. No. 4,044,611, Kaname et al., for recording water temperature, salinity, etc. The device is deployed from a ship and upon sensing various parameters, sends acoustic waves with such information back to the ship. The probe is designed to produce a stable rate of fall through the water, and to control the directional pattern of the sound wave generated into the surrounding water.
Finally, while not an oceanographic sensor, U.S. Pat. No. 4,631,956, Walden et al., discloses an airplane deployed oceanographic mooring device. The device comprises a detachable parachute, a surface float, a subsurface buoy, an anchor shell and a bottom finder.
While the devices described above all work well for their intended purpose, they fail to address the problem solved by the present invention. While it may be of interest to know certain water characteristics at any one instant in time, for a particular depth in the ocean, it is of far greater interest, and value, to have a profile through the ocean, from water surface to ocean floor of the relevant water characteristics. In addition to the top-to-bottom profiles, long-term measurements of conditions on the ocean floor and ocean surface are of interest. An expendable, remote sensor package capable of doing both would find immediate application in both civilian and military applications.
Therefore, a need exists for a simple and inexpensive device which can be deployed from either a ship or an airplane, and which is capable of making and storing measurements of water characteristics. Such device should be capable of making surface-to-floor and floor-to-surface profile measurements, as well as long-term measurements on the ocean floor and surface. Finally, the device should have transmitting capabilities to uplink the data to a satellite orbiting overhead.